Understanding the - Symbol - First Grade Mathematics
Just like addition has its trusty plus sign (+), subtraction has its own famous mathematical tool: the minus sign (-). The minus sign is one of the simplest symbols in the world to draw, but it carries immense power. When a minus sign appears between two numbers, it tells your brain to take away, subtract, or find the difference between the two quantities. In this chapter, you will learn the history and meaning of the minus symbol, understand how to read subtraction equations, and learn the special names for each part of a subtraction sentence.
The Minus Sign (-): A Single Horizontal Dash
The minus sign is a single straight horizontal stroke drawn neatly between two numbers.
The Minus Sign (-):
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Means: "SUBTRACT", "TAKE AWAY", "MINUS", "DIFFERENCE"
What the Minus Sign Tells You to Do
When you see 7 - 2, the minus sign gives you a direct command: "Start with 7, and remove 2 from it!" It tells you that the quantity on the right is being taken away from the quantity on the left.
Do Not Confuse with Plus!
Look at them side by side: Plus (+) has two crossing lines; it joins things together and makes them grow. Minus (-) has only one flat line; it takes things apart and makes them shrink.
The Anatomy of a Subtraction Equation
Every number in a subtraction equation has a formal mathematical name and a specific job.
Anatomy of a Subtraction Equation:
9 - 4 = 5
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Minuend Subtrahend Difference
(Whole) (Part) (Part)
The Minuend (The Starting Whole)
The first number in a subtraction sentence is called the minuend. It represents the total amount you begin with before anything is removed. In first grade subtraction, the minuend is always the largest number in the equation.
The Subtrahend (The Part Being Subtracted)
The second number, sitting right after the minus sign, is called the subtrahend. It tells how many items are being taken away or subtracted.
The Difference (The Result)
The number that sits after the equal sign is called the difference. It tells how many items remain in the group, or the gap between the two amounts.
Reading Subtraction Equations Aloud
Mathematicians read subtraction sentences using clear, precise words.
Reading Aloud:
Equation: 8 - 3 = 5
Way 1: "Eight minus three equals five."
Way 2: "Eight take away three leaves five."
Way 3: "The difference between eight and three is five."
The Order Matters in Subtraction!
In addition, you can switch the numbers (3 + 5 is the same as 5 + 3). But in subtraction, ORDER MATTERS! If you have 5 cookies, you can take away 2 cookies (5 - 2 = 3). But if you only have 2 cookies, you CANNOT take away 5 cookies! You cannot take away more than you have. Therefore, 5 - 2 is NOT the same as 2 - 5!
Practice Exercises
Exercise 1: Draw the minus symbol (-) and write two different phrases you can say out loud when reading it.
Exercise 2: In the equation 10 - 4 = 6, identify which number is the starting whole (minuend), which number is the part taken away (subtrahend), and which number is the difference.
Exercise 3: Explain why 7 - 3 is not the same as 3 - 7.
Exercise 4: Write a subtraction equation for this story: "There were 8 birds on a fence. 2 birds flew away. 6 birds stayed on the fence."
Solutions and Explanations
Solution to Exercise 1: The minus symbol is drawn as a single horizontal line segment: -. Two common phrases for reading it are "minus" and "take away."
Solution to Exercise 2: In the equation 10 - 4 = 6, the number 10 is the minuend (the starting whole), 4 is the subtrahend (the part taken away), and 6 is the difference (the result).
Solution to Exercise 3: 7 - 3 means starting with 7 items and taking away 3, which leaves 4. But 3 - 7 means starting with only 3 items and trying to remove 7, which is impossible with physical objects because you do not have enough items to take away. Order matters in subtraction!
Solution to Exercise 4: The subtraction equation is 8 - 2 = 6.